Burnishing apparatus



Dec. '1, 1936.

J. M. CHRISTMAN ,0 ,699

'BURNISHING APPARATUS Fild May 4, 1934 2 Sheets-Sheet l Dec. 1, 1936.CHRISTMAN 2,062,699

BURNISHING APPARATUS Filed May 4, 1934 2 Sheets-Sheet 2 Patented Dec. 1,1936 UNITED STATES nrmmsnmo APPARATUS John M. Christman, Detroit, Mich,assignor to Packard Motor Car Company, Detroit, Mich, a corporation ofMichigan Application May 4, 1934, Serial No. 723,987

17 Claims. (Cl. 29- 27) This invention relates to a method of andapparatus for burnishing machine elements, and is more particularlyconcerned with the burnishing of the circumferentially toothed rollerscommonly employed in automobile steering gear for engagement with andoperation by the usual worm at the lower end of the steering column.These rollers are employed in lieu of the more conventional worm gear orsector for the purpose of reducing friction in the steering gear.

It is of course essential that proper meshing of the roller with theworm be eifected and accurate and smooth finishing of both the rollerand the worm is important. By the present invention it is possible toproduce true and extremely smooth working surfaces on the teeth of theroller and at the same. time vto harden and toughen these surfaces, theresult of the burnishing operation being much more satisfactory so inthese respects than if grinding of the roller is' resorted to. Theinvention contemplates the employment of two or more master rollerswhich are grooved to receive the teeth of the roller to be burnished andwhich are suitably hardened,

the roller to be burnished being received between these master rollersand being rotated with the simultaneous application of pressure thereto.

- It is a more specific object of the invention to provide a pluralityofmaster burnishing rollers which are so supported and position'ed'thatthe roller to be burnishedcan be readily located therebetween and therequisite degree of pressure applied, means being provided whereby thisdegree of pressure may be predetermined.

In one embodiment of the invention a machine capable of automaticoperation is contemplated, the stock from which the rollers are formedbeing periodically advanced and the rollers being successively completedby grooving the stock, burnishing the grooved stock, and severing theburnished roller. Preferably the grooving and severing operations arecombined, one roller being severed simultaneously with the grooving ofthe stock to form the succeeding roller by a single 45 13001.

Figure 2 is an end elevation partly in section of'a portion of theconstruction sh wn in Fig- 55 i I Further objects and features of theinvention Figure 3 is a side elevation corresponding to Figure 2;

Figure 4 is a plan view of a'modified type of machine capable of bothforming and burnishing the rollers;

Figure 5 is an end elevation of the structure shown in Figure 4;

Figure 6 is a sectional view of one type of steering gear illustratingthe manner in which the product of the machine disclosed herein may 10.

', In the form of the invention shown in Figure 1 of the drawings, aconventional machine of the I adjustable bed type is disclosed, thismachine comprising a base l0 having a standard 12 rigid therewith andextending vertically therefrom, and 25 a bed or table I 3 supported onthe base III for movement in several directions with respect thereto.Secured rigidly to the table I3 is a carrier M on which are joumalledfor rotation a plurality of master rollers l6 and I1, preferably 30 twoin number as illustrated in the drawings. An arm l9 rigid with anddependent from the standard l2 carries a third master roller 20 which isjoumalled for rotation on the arm I9, for instance by means-of a shaft2| extending through the arm and rotatable by a pu ley 24, the pulleyand roller 20' being secured to-the shaft. The axes of the masterrollers l6, l1, and 20 are parallel and preferably horizontal, the axisof the roller 20 being shown as located above the axes of the rollers Itand I1. It will nevertheless be ,understood that this arrangementis byno means essential and that the relative positions of these rollers maybe altered as desired so long as the axes thereof remain substantiallyparallel. It is convenient, howe ver, in describing and defining theinvention to refer to the rollers l6 and H as located beneath the roller20.

The carrier M for the rollers l6 and H ma be secured to the bed l3 bybolts 22 passing through the base '23 of the carrier and threaded in thebed, locating keys 25 secured to the carrier and engagingcorresponding'grooves 26 in the bed being provided to ensure that thecarrier will not be twisted on the bed during operation of the machine.

The carrier i4 and the bed I3 are displaceable in. a plane substantiallyperpendicular to the axes of the rollers l6, l1, and 20, and for thispurpose are supported for sliding movement on a member 21; displacementof the bed and carrier and retention thereof in any desired position ofadjustment beingeifected by the threaded rod 29 operable by the handle30 in the conventional manner. It will be observed that the axis of theroller 16 is spaced to a suflicient extent from the axis of the roller20 to permit the roller l6 to move under the roller 23 from one sidethereof to. the other, movement of the carrier and bed to. the rightbeing limited by the engagement of abutments 32 and 33 on the bed andthe member 21 respectively. One of these abutments is adjustable in thedirection of displacement of the bed. Thus the abutment 32 may besupported on the bed l3 by means of a bolt 35 extending through a slot36 in the bed so that the abutment may be displaced along the slot 36and may be clamped in any desired position.

The member 21 is preferably, although not necessarily, supported forsliding movement in the axial direction of the rollers l6, l1, and 20,for instance on a member 38, suitable screw and nut gearing actuable bythe handle 39 being provided to adjust the position of the member 21.The member 38, and the elements of the machine sup-' ported thereby,including the table I3, are ad- Justable vertically, being preferablyguided in this vertical movement on the standard H2 in the conventionalmanner. This vertical movement may be efiected by means of a threadedshaft 40 engaginga nut 4| carried in the base Ill, the shaft 40 beingjoumalled in the member 38 as indicated at 42 and being rotatable bybevel gearing 44 which is in turn actuated by. the handle 45.

, The structure thus far described for effecting relative adjustment ofthe axes of the roller 23 and of the rollers l6 and I1 is conventionaland the details thereof form no essential part of the present vention.Such arrangements are commonly foun in milling machines and the likewhich ordinarily-provide for vertical adjustment as well as horizontaladjustment in two directions of a work table or other support.

The master rollers I 8, l1, and 20 are preferably similar so far as theconfiguration of their circumferentially' toothed portions is concernedalthough they may differ in diameter. It will be observed that eachroller is grooved as indicated at 48, two grooves being provided toaccommodate and to receive in interlocking relation the teeth 49 on theroller 50 to be burnished which are shown more particularly in Figures3, 6, and 7 of the drawings, it being apparent that the number ofgrooves provided in the master rollers will equal the number of teethformed on the roller t].

While in the preferred form of the invention a roller having twocircumferential teeth is formed, rollers having a less or greater numberof teeth can obviously be burnished by the same operation. I V

The machine thus far described is initially adjusted so as to permit theburnishing of rollers in rapid succession with the least possible delay.Thus the handle 39 is operated to align the rollers l6, I1, and 20 in anaxial direction, the correct relative position being indicated in Figure2 of the drawings. The handle 45 is then operated to raise or lower thetable l3 and the carrier M to the proper vertical position, thisposition being determined by displacing the carrier l4 laterally untilthe roller I3 is directly beneath the roller 20 and inserting a gauge orfeeler 52 between these rollers to determine the correct spacingthereof. The carrier I4 is then displaced to the right by operation ofthe handle 30 to a position in which the rollers l1 and 20 are spaced bythe thickness of the gauge or feeler 53 as shown in Figure 1 of thedrawings. The abutment 32 is then engaged with the abutment 33 andsecured in position on the table, it being observed that displacement ofthe table and carrier M to the right on each operation is therebylimited.

The handle 30 is then manipulated to displace the table l3 and carrier Mto the left, a roller 50 to be burnished is placed in position betweenthe master rollers l6 and ll, and the table and carrier are thendisplaced to the right to bring the roller 50 into engagement with themaster roller 20 and apply the necessary pressure between all of therollers, the shaft 2| being simultaneously rotated and the masterrollers and the roller 50 being rotated thereby. If desired the rollersmay be cooled during the burnishing operation by causing flow of liquidsuch as oil over the same. On completion of the operation, the table andcarrier are moved once more to the left and the burnished roller 5!!replaced by the succeeding roller, the foregoing operations being thenrepeated.

Obviously a machine of this character can be made entirely automatic,the lateral displacement of the table and carrier from the operative tothe inoperative position and vice versa being effected by suitablydesigned cams, and the rollers 50 being successively delivered andremoved from the carrier by conventional automatic feeding mechanism, itbeing only necessary to make slight adjustments from time to time tocompenthese rollers.

When formed in this way, the rollers 50 will mesh accurately withhour-glass worms such as shown at 46 in Figure 6 of the drawings, theroller being preferably supported for rotation on an axis 5| parallel-to the worm in a carrier 54, the latter being in turn rotatable aboutan axis perpendicular to the axis of the roller in an arm 51, thissecond rotational axis being provided to accommodate the roller to thevarying helix angle of the worm. The arm 51 constitutes in effect theequivalent of the usual worm gear and is connected in the conventionalmanner to the steerable road wheels of the vehicle. The structure shownin Figure 6 forms no part of the present invention and is included tofacilitate an understanding of the nature of the rollers 50 and theirfunction.

Referring now more particularly to the form of the invention shown inFigures 4 and 5, it will be observed that the rollers 50 arevillustrated as formed on stock 55, the latter being secured in androtated by a suitable work holder 56. While the work holder56 is showndiagrammatically in the drawings to simplify the description andillustration of the invention, I may use for this purpose a conventionaltype of screw machine which is automatically operable in known manner toperiodically advance the stock axially and to rotate the stock,theperiodical advance being effected by suitably designed cams or thelike.

At one side of the stock a carrier 58 is provided, this carrier beingsecured to a table 59 which is in turn supported on a base 60 forsliding movein which are supported for rotation two or more masterrollers, of which three are preferably provided, these rollers beingdesignated 64, 65, and 66. The axes of the rollers are parallel to theaxis of the stock and may be so relatively positioned that as a roller50 to be burnished passes between the rollers 64 and 86 and intoengagement with the roller 65 with the desired pres-- sure,substantially equal pressure will be applied thereto by the rollers 64and 66.

At the other side of the stock a device for forming and preferably forcutting ofi the rollers is disposed, this device consisting of; a table58 which is mounted for sliding movement on the support 60 transverse ofthe axis of the stock 55 and which has rigidly secured thereto a toolsupporting bracket 10, the latter carrying a-tool 'H formed as shownmore particularly in Figure 4 of the drawings with two cutting edges 12,

adapted to form corresponding grooves in thestock, and a severing edgell adapted to remove a formed and burnished roller from the stock.

The bumishing device and the cutteror grooving device are alternatelybrought into engagement with the s eck 55 by lateral displacement withrespect th etc, a common operating means being preferably provided.Thus'nuts l6 and 11 may depend from the bumishing device and thegrooving device respectively, these nuts being engaged by a threaded rod19 supported in any suitable manner for rotation and against length-"'wise displacement in the base 60, a handle 80 being provided to effectrotation of the rod and simultaneous displacement of the two devices inthe same direction.

With the parts in the position shown in Figure 4, the stock 55 isadvanced axially through a distance corresponding to. the length of theelement which may be assumed to have been formed and burnished. Thecutting device is then displaced to the left to engage the stock,

plete the bumishing operation, the bumishing device and the-cuttingdevice being thereupon displaced to the left and the stock againadvanced while disengaged from both devices as hereinbetore explained. I

In order that the pressure applied by the master rollers to the rollerto beburnished maybe determined in advance, an arrangement similar tothat shown in Figure 1 may be provided; thus" abutments 82 and 83located on the table 59 and the base 50 respectively may be employed,Once! these abutments being adjustable. v

The entire operation of the machine shown in Figures! and 5 may beautomatic, displacement;

oi the bumishing device and the cutting device being effected bysuitable mechanism serving toperiodically rotate the threaded rod I9 intimed relationwith the axial advance of the st'ock 55. In thisconnectionit may be pointed out that the displacement of the bumishing rollerswith re- 1 spect to the stock is relative, that is to say. the

stock may be displaced laterally while the burnishing rollers and thecutting device "are maintained in a stationary position. Similarly, inthe three master elements.

first described form of the invention) the masterezzz roller 20 may bedisplaced laterallyoi'the axis thereof while the rollers it and H areretainedagainst movement. Various other changesin the structure hereindescribed will occur to one skilled -in the art to which the inventionrelates and all modifications are contemplated such as fallwithin thescope of the appended claims. Having thus described the invention, whatis claimed as new and desired to, be secured by Letters Patent is: J 1.In apparatus for bumishing circumferentiall'y toothed elements, the'combination with a support, of a circumferentially toothed masterelement rotatably mounted on said support, at

least two master elements carried by said support for rotation aboutspaced axes parallel to the axis of said first named element and forlateral displacement with respect to said first named element, saidmaster elements receiving therebetween a circumferentially, toothedelement to be burnished, means for imparting relative lateraldisplacement to said second named master elements' and said first namedmaster element to apply pressure in agenerally radial'direction to theelement to be burnished, and means for rotating said elements.

2. In apparatus .for bumishing circumferen tially toothed elements, thecombination with a support, of a circumferentially toothed masterelement rotatably mounted on said support, at least two master elementscarried by-said support for rotation about spaced axes parallel to theaxis of said first named element and ,for lateral rectilineardisplacement as a unit with respect to said first named element, saidmaster elements receiving therebetween a circumferentially toothedelement to be burnished, means for imparting relative lateraldisplacement to said second named master elements and said firstnamedmaster element to apply pressure in a generally and means forrotating saidelements.

3. In apparatus for bumishing circumferentially toothed elements, thecombination with a support, of a circumferentially toothed master'element rotatably mounted on said support, two master elements carriedby said support for rotation about spaced-axes parallel to the axis ofsaid first named element and for lateral rectilinear displacement as aunit with respect to said first named element, said master elements re-.radial direction to the element to be burnished,

ceiving therebetween a circumferentially toothed element to bebur'nished, means for imparting relative lateral displacement to said.second named master elements and said first named master element toapply pressure in a generally radial direction-to the element to'beburnished, and means for rotating said elements, one only of said twosecond named master elements being so positioned as'to permitdisplacement thereof to a position adjacent either side of'said first"named master element to facilitate the position-.

ing of the elementto'be burnished between the 4. In apparatus forbumishing circumi erenr tiallytoothed elements, the combination with a asupport, of a circumterentially toothed master element rotatably mountedon said support, a

carrier laterally 'displa'ceable on, said support with respect to saidmaster element, two circumferentially toothed master elements supportedfor rotation on said carrier about axes parallel to. the",

axis-oi said first named'master element, the plane elements and theelement to be burnished in directions generally radial of the latter,and means for supporting and rotating the element to be burnished,whereby said master elements are rotated therefrom, said last namedmeans comprising a rotatable stock holder for supporting and rotatingthe stock on which the element to be burnished is formed, and means forengaging and simultaneously forming an element on said stock andsevering the preceding burnished element from the stock.

16. In apparatus for burnishing circumferentially toothed elements, thecombination with a support, of a plurality of circumferentially toothedmaster elements carried by said support for rotation about parallel axesand receiving the toothed element to be burnished.- therebetween, meansfor applying pressure between said master elements and the element to beburnished in directions generally radial of the latter, said meanscomprising a relatively laterally displaceable support for the elementvto be burnished, and an adjustable stop means for limiting the relativedisplacement of said said supports to limit the I pressure applied tosaid elements.

1'7. In apparatus for burnishing circumferentially toothed elements, thecombination with a support, of a plurality of circumferentially toothedmaster elements carried by said support for rotation about parallel axesand receiving the toothed element to be burnished therebetween, meansfor applying pressure between said master elements and the element to beburnished in directions generally radial 01' the latter, said meanscomprising a relatively laterally displaceable support for the elementto be burnished, and an adjustable stop means for limiting the relativedisplacement of said supports to limit the pressure applied to saidelements, said support for the element to be burnished being rotatable,whereby said master elements may -be rotated therefrom.

JOHN M. CHRISTMAN.

